For oil recovery a well is drilled and a well tubular may be introduced into the well bore. The outside diameter of the well tubular is smaller than the inside diameter of the wellbore, thereby forming an annular space between the well tubular and the wellbore (see FIG. 1). The well tubular is typically perforated at one or more zones in order to facilitate the flow of hydrocarbons into the tubular and subsequent flow upstream for recovery. Occasionally contaminating materials such as water and sand are produced along with the hydrocarbons from a part of the subterranean formations surrounding the well tubular. In these situations it may be desirable to seal off the well tubular from one or more parts of the annular space. This is just one example. There are also other situations, where it may be desirable to provide a sealing of the annular space.
One way of sealing off an annular space is to employ an external casing packer, which consist of a hollow rubber element, which is inflated by a fluid, e.g. concrete, which is injected by a tool. After injection, the concrete sets and keeps the rubber element in the inflated position, in which it seals between the tubing and the well bore wall. This type of packer is encumbered with the drawback that the rubber element may be damaged during the installation or inflation. Further, in an open well bore, it may also have an unsatisfactory sealing function if the geometric shape of the well's wall is enlarged beyond the outer dimension of the packer, such as in a washed out well bore.
To seal off e.g. an open (uncased) or cased wellbore, another possibility is to isolate the internal part of the well tubular using packers. Cement or another hardenable composition is then pumped down to the isolated zone to seal the perforated openings in the desired part of the well tubular.
However, materials such as cement do not have the appropriate physical properties to spread evenly into the annulus and seal off a tubular hole, in particular in deviating wells, such as horizontal wells. It is therefore required to pump large quantities of cement in order to be sure that a hole is effectively sealed or to isolate the internal part of the well tubular using temporary packers. This is both time consuming and expensive. The use of cement is also a more permanent solution since the cement will fill a large portion of the annulus between the production tubing and the casing due to excessive axial dispersion, thereby making it near to impossible to remove the production tubing if desired.
U.S. Pat. No. 4,972,906 titled “Method for selective plugging of a zone in a well” to Conoco Inc. describes the use of a mixture of a liquid epoxy material and a hardener for plugging a zone in a subterranean zone. The epoxy material used is heavier than the fluid in the well, and it is further characterized as being free of solids and having a low viscosity at downhole temperature and pressure. The material is placed in a well by the use of a positive displacement bailer. Hence, the liquid epoxy material exhibit an undesirable axial dispersion which may only partially be overcome by using an excessive amount of the epoxy material. Additionally the well should preferably remain dormant during the placement of the epoxy material and until it has hardened, and means to minimize or eliminate fluid flow, i.e. cross flow, should be employed. Thus, the method has the drawback of not facilitating a site-specific placing of the seal. Additionally the method suffers the drawback that it only works on essentially dormant wells, i.e. not experiencing a cross flow, and it does not solve the problem of setting a packer in an essentially solid free annulus, nor does it solve the problem of setting a packer in a deviating well, which is not vertical.
WO 2009/109625 A1 titled “Method for sealing an annular space in a wellbore” to Mærsk Oil and Gas A/S describes a method for providing an annular seal, which may be epoxy, phenolic or polyester based comprising at least one component and having physical and fluid dynamic properties compatible with the temperature, pressure and earth formation properties downhole. WO 2009/109625 A1 covers a great many possibilities for providing a sealing substance which is compatible with the temperature, pressure and earth formation properties downhole. However, WO 2009/109625 A1 is silent about any particular set of parameters resulting in the improved sealing fluids of the present invention.
In particular WO 2009/109625 A1 is silent about parameters that improve the sealing properties and/or reduce the axial dispersion, in particular how to solve the problem of obtaining a seal in a situation where the annulus has an active crossflow and/or how to set a packer in a deviating well.
Hence, there is a need for an improved method for setting a packer in an annulus between a well tubular and a wellbore. A need further exists for a method for setting a packer in an uncased wellbore. A need further exists for a method that reduces the axial dispersion of the sealing fluid that forms the packer in situ. A need further exists for a method for setting a packer in an annulus experiencing an active cross flow. A need further exists for a method for setting a packer in an annulus which is eccentric. A need further exists for a method for setting a packer in an annulus of a deviating well, such as a horizontal well.